DE102019205488A1 - Subscriber station for a serial bus system and method for communication in a serial bus system - Google Patents

Abstract

A subscriber station (10; 20; 30; 1 to 4) for a serial bus system (100) and a method for communication in a serial bus system (100) are provided. The subscriber station (10; 20; 30; 1 to 4) has a communication control device (11; 21; 31) for controlling communication between the subscriber station (10; 20; 30; 1 to 4) with at least one other subscriber station (10; 20; 30; 1 to 4) of the bus system (100), a transmitting / receiving device (12; 22; 32) for transmitting a transmission signal (TX1; TX2; TX3; TX4) generated by the communication control device (11; 21; 31) in one Frame (450; 460) on a bus (40) of the bus system (100), and a time planning unit (15; 25; 35) for planning a temporal access of the subscriber station (10; 20; 30; 1 to 4) to the bus ( 40) in at least one time slot (S1 to S4) of a round (C) of successive time slots (S1 to S4), with each subscriber station (10; 20; 30; 1 to 4) of the bus (10; 20; 30; 1 to 4) in a round (C) 40) at least one time slot (S1 to S4) is provided for sending its transmission signal (TX1; TX2; TX3; TX4) and the round (C) is repeated cyclically, and wob ei the scheduling unit (15; 25; 35) is designed to use at least one item of information received from the bus (40) to determine an assignment which defines which time slot (S1 to S4) of the round (C) the transmitting / receiving device (12; 22; 32) for Sending the frame (450; 460) for the transmission signal (TX1; TX2; TX3; TX4) on the bus (40) is allowed to use.

Description

Technical area

The present invention relates to a subscriber station for a serial bus system and a method for communication in a serial bus system with which communication is possible for real-time-critical applications.

State of the art

For the communication between sensors and control units, for example in vehicles, for cost reasons, instead of a point-to-point connection, a bus system is currently being used more and more frequently, in which data as messages in the ISO11898-1: 2015 standard as a CAN protocol specification with CAN FD are transferred. The messages are transmitted between the subscriber stations of the bus system, such as sensors, control units, transmitters, etc. Here, CAN FD is currently used in the introductory phase in the first step mostly with a data bit rate of 2 Mbit / s for the transmission of bits of the data field and with an arbitration bit rate of 500 kbit / s for the transmission of bits of the arbitration field in the vehicle.

To avoid collisions of messages from different subscriber stations on the bus, the CSMA / CR method (CR = Collision Resolution) is used with CAN. This resolves collisions with so-called arbitration at the beginning of a message or a frame. In the case of arbitration, an identifier (identifier = ID) is evaluated to determine which message may be sent next. The message or the frame that has the identifier with the highest priority prevails. This corresponds to strict priority scheduling. This is sufficient for many applications in the autonomous vehicle.

However, the arbitration means that current CAN-based bus systems cannot currently be used for applications that require 100% deterministic bus access, i.e. a guarantee that a subscriber station of the bus system can definitely send a message or a frame at a certain time is.

Disclosure of the invention

It is therefore the object of the present invention to provide a subscriber station for a serial bus system and a method for communication in a serial bus system which solve the aforementioned problems. In particular, a subscriber station for a serial bus system and a method for communication in a serial bus system are to be provided which can be used in communication for real-time-critical applications and in which, in particular, 100% deterministic bus access is possible.

The object is achieved by a subscriber station for a serial bus system with the features of claim 1. The subscriber station has a communication control device for controlling communication of the subscriber station with at least one other subscriber station of the bus system, a transmitting / receiving device for transmitting a transmission signal generated by the communication control device in a frame on a bus of the bus system, and a time planning unit for planning a time access of the Subscriber station on the bus in at least one time slot of a round of consecutive time slots, with at least one time slot being provided in a round for each subscriber station of the bus for sending its transmission signal and the round being repeated cyclically, and the scheduling unit being designed using at least to determine an assignment of information received from the bus which defines which time slot of the round the transmitting / receiving device is allowed to use to transmit the frame for the transmission signal on the bus.

In a bus system to which the subscriber stations described above are connected, it is ensured that each subscriber station is deterministically on the bus
can access. As a result, each of the subscriber stations receives a guaranteed minimum communication bandwidth on the bus, at least for the time in which the bus is to be accessed deterministically. This means that real-time-critical applications can also be implemented with a CAN-based bus system.
The subscriber station can be used with any communication protocol that works according to the CSMA / CR method, for example with any CAN-based communication protocol, but in particular with CAN XL, a CAN FD successor.

In the case of the subscriber station described, it is also very advantageous that the function of deterministic scheduling, which can also be referred to as “deterministic scheduling”, can be activated for deterministic bus access when required, even during operation. As a result, the subscriber station is designed to carry out two different communication methods, namely to carry out either a CSMA / CR method that implements “strict priority scheduling” or a CSMA / CR method with additional deterministic scheduling. This is a great advantage over bus systems in which only one of the communication methods mentioned is possible, such as 10BASE-T1S, Flexray, etc. Another very great advantage is that the approach described here is much easier to configure and use than with previous methods.

The subscriber station described is designed in such a way that, together with the other subscriber stations on the bus, it organizes which subscriber station is allowed to send the next message. As a result, the configuration of the subscriber station and the associated bus system is self-organizing. This makes the configuration very uncomplicated. As a result, there is hardly any additional training effort for staff to configure the bus system and the subscriber station.

An additional advantage of the subscriber station is that no “single point of failure” is possible, as is the case with the master node required for 10BASE-T1S. This means that if a subscriber station fails due to a defect and therefore no longer sends anything, this has no negative effects on communication on the bus.

Depending on the implemented variant of the deterministic time planning, the subscriber station can either deliver the same maximum delays (worst-case delays) as PLCA from 10BASE-T1S or approximately 50% shorter maximum delays (worst-case delays) than PLCA from 10BASE-T1S.

In addition, it is possible to expand the subscriber station with many additional functions depending on the application or request, since the arbitration is always available. For example, it is possible to use an unused time slot of another subscriber station of the bus system for sending. It is also possible that a weighted cyclical sending (weighted round robin) is implemented, in which some subscriber stations are allowed to send more messages per cycle or round than other subscriber stations. Another option is that a subscriber station of the bus system can also send several shorter messages in its time slot, which is also called slot, instead of one message of maximum length. This enables fairness with regard to the bandwidth available on the bus, instead of only with regard to the number of messages sent or sendable by each subscriber station.

As a result, the subscriber station can send and receive messages with great flexibility with regard to bus access, and thus a very wide range of quality of service requirements and thus also applications can be implemented.

Advantageous further refinements of the subscriber station are given in the dependent claims.

Possibly the at least one piece of information received from the bus is a frame notifying the start of the round, the at least one piece of information received from the bus also being a frame identifier and / or an assignment of the time slots of a round to the subscriber stations of the bus and / or the Information includes which of the subscriber stations of the bus is currently transmitting.

According to an exemplary embodiment, the time planning unit is designed to use at least the frame informing the start of the round as the at least one item of information received from the bus and to evaluate a frame identifier of a sender of a frame received from the bus.

According to another exemplary embodiment, the time planning unit is designed to evaluate a data field of the frame informing the start of the round in which the at least one item of information received from the bus is arranged.

According to yet another exemplary embodiment, the time planning unit is designed to wait until the communication control device has received a frame from the bus that notifies the start of the round, and then to determine which of the other subscriber stations of the bus is operating the bus system using a priority of the transmission signal Time slot of the round the transmitting / receiving device is allowed to use to transmit the frame for the transmission signal on the bus.

It is conceivable that the communication control device is configured to divide the frame into a first communication phase and a second communication phase at least in a switch-on phase of the bus, with which of the subscriber stations of the bus is negotiated in the first communication phase in the subsequent second Communication phase gets an at least temporarily exclusive, collision-free access to the bus.

The number of time slots per lap is possibly greater than the number of time slots that are assigned to the subscriber stations of the bus per lap, with which of the subscriber stations of the bus is negotiated in the first communication phase in a time slot that is not assigned to any of the subscriber stations of the bus Bus gets an at least temporarily exclusive, collision-free access to the bus in the subsequent second communication phase.

The minimum duration of a time slot can optionally be selected as a bit time of a bit in the first communication phase. Here, the scheduling unit is optionally designed to send a frame in a time slot assigned to the subscriber station with a priority that is higher than a priority of a frame which the scheduling unit is designed to send in a time slot that of another subscriber station of the bus.

Alternatively, it is conceivable that the minimum duration of a time slot is two bit times of a bit of the first communication phase, the time planning unit being designed to enable the subscriber station to access the bus in the second bit of a time slot of the round when the subscriber station or another subscriber station of the bus in the first bit of the time slot lets its transmission opportunity pass unused.

According to a special embodiment variant, the time planning unit has a counting module which is designed to increment its count value for each frame received by the bus and to increment it for each transmission opportunity that has passed unused for a time slot, the counting module being designed to set its count value to 1 when the frame notifying the start of the round has been received.

The counting module can be designed to increment its count value for each frame received by the bus after receiving a bit which signals the start of a frame, even if the frame is later aborted by the subscriber station sending the frame due to an error. In this case, the time planning unit can be designed to enable the subscriber station to access the bus for the next time slot of the round if the count value of the counting module is equal to the number of the time slot assigned to the subscriber station.

According to one exemplary embodiment, the time planning unit is designed to enable temporal access by the subscriber station to the bus in a time slot of the round if another subscriber station on the bus lets its transmission opportunity pass unused.

Possibly the communication control device is designed to arrange a subscriber station number in the transmission signal which is exclusively assigned to the subscriber station on the bus, the time planning unit being designed to enable temporal access of the subscriber station to the bus in the time slot of the round assigned to the subscriber station if the time planning unit can evaluate a subscriber station number in a frame received from the bus. In this way, the time planning unit can use this information to determine its own time slot.

In one embodiment, the number of time slots that are assigned to the subscriber station per lap can be at least temporarily unequal to a number of time slots that are assigned to another subscriber station of the bus per lap.

In another embodiment, the subscriber station can be configured to send more than one frame on the bus per time slot. Additionally or alternatively, the number of frames that the subscriber station is allowed to send on the bus per time slot is at least temporarily unequal to a number of frames that another subscriber station of the bus is allowed to send on the bus per time slot.

Optionally, the communication control device is designed to send a dominant pulse at the beginning of a recessive bit in the time slot assigned to the subscriber station, which is shorter than the bit time of the recessive bit if the communication control device lets its transmission opportunity pass unused.

According to another option, the subscriber station is designed in such a way that the time planning unit can be switched on or off depending on the time requirements for communication on the bus, or that an operating mode of the time planning unit can be changed by configuring predetermined parameters during operation of the bus system, the Operating mode of the scheduling unit defines a predetermined mode of communication on the bus.

At least two of the subscriber stations described above can be part of a bus system which also comprises a bus, the at least two subscriber stations being connected to one another via the bus in such a way that they can communicate with one another serially. Here, at least one of the subscriber stations can be a master subscriber station for sending a frame which informs the at least two subscriber stations of the start of a round of communication on the bus,
at least one backup master optionally being provided for additionally performing the function of the master subscriber station on the bus. A subscriber station can thus act as a subscriber and as a master at the same time.

The aforementioned object is also achieved by a method for communication in a serial bus system according to claim 20. The method is carried out with a subscriber station of the bus system, which has a communication control device and a transmitting / receiving device, the method comprising the steps of controlling, with a communication control device, communication of the subscriber station with at least one other subscriber station of the bus system, and sending with a transmitting / receiving device, a transmission signal generated by the communication control device in a frame on a bus of the bus system according to the planning of a time planning unit, which plans a time slot of the subscriber station on the bus in at least one time slot of a round of successive time slots, in one Round for each subscriber station of the bus at least one time slot is provided for sending its transmission signal and the round is repeated cyclically, and wherein the time planning unit using at least one received from the bus formation determines an assignment that determines which time slot of the round the transmitting / receiving device is allowed to use to transmit the frame for the transmission signal on the bus.

The method offers the same advantages as mentioned above with regard to the subscriber station.

Further possible implementations of the invention also include combinations, not explicitly mentioned, of features or embodiments described above or below with regard to the exemplary embodiments. The person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the invention.

Figure list

• 1 ein vereinfachtes Blockschaltbild eines Bussystems gemäß einem ersten Ausführungsbeispiel;
• 2 ein Schaubild zur Veranschaulichung des Aufbaus von Nachrichten, die von Teilnehmerstationen des Bussystems gemäß dem ersten Ausführungsbeispiel gesendet werden können;
• 3 ein Zeitdiagramm zur Veranschaulichung des Ablaufs einer Kommunikation in dem Bussystem gemäß dem ersten Ausführungsbeispiel;
• 4 ein Zeitdiagramm zur Veranschaulichung des Ablaufs einer Kommunikation in dem Bussystem gemäß dem ersten Ausführungsbeispiel, nachdem eine Teilnehmerstation wieder aufgeweckt wurde;
• 5 ein Zeitdiagramm zur Veranschaulichung des Ablaufs einer Kommunikation in einem Bussystem gemäß einem zweiten Ausführungsbeispiel;
• 6 ein Zeitdiagramm zur Veranschaulichung des Ablaufs einer Kommunikation in einem Bussystem gemäß einem dritten Ausführungsbeispiel;
• 7 ein Zeitdiagramm zur Veranschaulichung des Ablaufs einer Kommunikation in einem Bussystem gemäß einem vierten Ausführungsbeispiel;
• 8 ein Zeitdiagramm zur Veranschaulichung des Ablaufs einer Kommunikation in einem Bussystem gemäß einem fünften Ausführungsbeispiel; und
• 9 einen zeitlichen Verlauf eines differentiellen Bussignals in ungenutzten Zeitschlitzen bei einem Bussystem gemäß einem sechsten Ausführungsbeispiel.

The invention is described in more detail below with reference to the accompanying drawings and using exemplary embodiments. Show it:

• 1 a simplified block diagram of a bus system according to a first embodiment;
• 2 a diagram to illustrate the structure of messages that can be sent by subscriber stations of the bus system according to the first embodiment;
• 3 a timing diagram to illustrate the sequence of communication in the bus system according to the first embodiment;
• 4th a timing diagram to illustrate the course of a communication in the bus system according to the first embodiment after a subscriber station has been woken up again;
• 5 a timing diagram to illustrate the sequence of communication in a bus system according to a second embodiment;
• 6 a timing diagram to illustrate the sequence of a communication in a bus system according to a third embodiment;
• 7th a timing diagram to illustrate the sequence of communication in a bus system according to a fourth embodiment;
• 8th a timing diagram to illustrate the sequence of communication in a bus system according to a fifth embodiment; and
• 9 a time profile of a differential bus signal in unused time slots in a bus system according to a sixth embodiment.

In the figures, identical or functionally identical elements are provided with the same reference symbols, unless otherwise specified.

Description of the exemplary embodiments

1 shows a bus system as an example 100 , which in particular is fundamentally designed as a CAN bus system and / or a CAN FD bus system and / or a CAN FD successor bus system, which is referred to here as a CAN XL bus system, and / or modifications thereof, as described below. The bus system 100 can be used in a vehicle, especially a motor vehicle, an airplane, etc., or in a hospital, etc.

In 1 has the bus system 100 a large number of subscriber stations 10 , 20th , 30th each to a bus 40 with a first bus vein 41 and a second bus core 42 are connected. The bus veins 41 , 42 CAN_H and CAN_L or CAN-XL_H and CAN-XL_L can also be called and are used for electrical signal transmission after coupling in the dominant level or generating recessive levels for a signal in the transmission state. About the bus 40 are news 45 , 46 in the form of signals between the individual subscriber stations 10 , 20th , 30th serial transferable. Occurs when communicating on the bus 40 an error, as indicated by the jagged black block arrow in 1 can optionally be an error frame 47 (Error Flag) are sent. The participant stations 10 , 20th , 30th are, for example, control devices, sensors, display devices, etc. of a motor vehicle.

As in 1 has shown the subscriber station 10 a communication controller 11 , a transmitting / receiving device 12 and a scheduling unit 15th with a counting module 151 . The participant station 20th has a communication controller 21st a transmitting / receiving device 22nd and a scheduling unit 25th with a counting module 251 . The participant station 30th has a communication controller 31 , a transmitting / receiving device 32 and a scheduling unit 35 with a counting module 351 . The transmitting / receiving devices 12 , 22nd , 32 of the subscriber stations 10 , 20th , 30th are each directly on the bus 40 connected even if this is in 1 is not illustrated.

The communication control devices 11 , 21st , 31 each serve to control a communication of the respective subscriber station 10 , 20th , 30th over the bus 40 with at least one other subscriber station of the subscriber stations 10 , 20th , 30th who got to the bus 40 are connected.

The communication control devices 11 , 31 create and read first messages 45 , which are, for example, CAN messages built on the basis of a CAN XL format that is related to 2 is described in more detail. The communication control devices 11 , 31 can also be designed to send a CAN XL message as required 45 or a CAN FD message 46 for the transmitting / receiving devices 12 , 32 to provide or to receive from it. The communication control devices 11 , 31 so create and read a first message 45 or second message 46 , being the first and second messages 45 , 46 differ by their data transmission standard, namely in this case CAN XL or CAN FD.

The communication controller 21st can be designed like a conventional CAN controller according to ISO 11898-1: 2015, in particular like a CAN FD tolerant Classical CAN controller or a CAN FD controller. The communication controller 21st creates and reads second messages 46 , for example Classical CAN messages or CAN FD messages 46 . With the CAN FD messages 46 A number from 0 to 64 data bytes can be included, which are also transmitted at a significantly faster data rate than with a Classical CAN message. In particular, the communication control device 21st except for the unit 25th designed like a conventional CAN or CAN FD controller.

The transmitting / receiving device 22nd can be designed like a conventional CAN transceiver according to ISO 11898-2: 2016 or CAN FD transceiver. The transmitting / receiving devices 12 , 32 can be run to messages as needed 45 or bits of a frame according to the CAN XL format or messages 46 or bits of a frame according to the current CAN FD format for the associated communication control device 11 , 31 to provide or to receive from it.

With the two participant stations 10 , 30th is a formation and then transmission of messages 45 with the CAN XL format as well as the receipt of such messages 45 realizable.

2 shows in its upper part for the message 46 a CAN FD frame 460 as received from the transceiver 12 or the transceiver 22nd or the transceiver 32 over time t serially on the bus 40 is sent. In the lower part of 2 is for the message 45 a specific example of a CAN-XL frame 450 shown as he is from the transceiver 22nd or 32 over time t serially on the bus 40 can be sent. Alternatively, the upper part of 2 as a Classical CAN frame and the lower part of 2 can be interpreted as a CAN FD frame or CAN XL frame.

According to 2 are the frames 450 , 460 for CAN communication on the bus 40 in different communication phases 451 , 452 , 453 divided, namely an arbitration phase 451 , a data phase 452 , and a frame end phase 453 . In the arbitration phase 451 at the beginning of the frame 450 , 460 transmits the associated transmitting / receiving device 12 , 22nd , 32 an identifier 451x and part of a control panel. In the data phase 452 Among other things, the following data is sent: a part of the control field, the user data of the CAN-XL frame or the message 45 , 46 in a data field DF and a checksum. With a frame 450 For example, part of the control field can be an optional data type field (DataType field) DT which indicates the type of data that is sent in the data field DF. The data type field DT is in 2 for illustration shown with a greater length than is often in relation to the length of the data field DF. The data type field DT can be in the control part of the frame 450 , 460 especially at the beginning of the data phase 452 , or at the end of the arbitration phase 451 be transmitted. After the data phase 452 , the frame end phase follows 453 , which according to ISO11898-1: 2015 also belongs to the arbitration phase. The frame end phase 453 which is also called the arbitration phase at the end of the frame 450 , 460 can be designated, has, inter alia, the following parts: an ACK field and an end of frame identifier (EOF). The Frame end phase 453 is not relevant here and is therefore not described in more detail.

In the arbitration phase 451 transmits the associated transmitting / receiving device 12 , 22nd , 32 Bits of the frame 450 , 460 at a slower bit rate than in the data phase 452 . With CAN FD is the data phase 452 versus the data phase 452 of the Classical CAN frame significantly reduced in time. In special applications, the two bit rates of the phases 451 , 452 can be configured to the same values, but usually the bit rate is in the data phase 452 much higher than in the arbitration phase 451 .

A frame format is defined for CAN XL in which not only the bit rates within the frame 450 or the message 45 can be switched, but optionally also the operating mode of the transmitting / receiving device 12 , 32 . In the arbitration phase 451 the transceiver works 12 , 32 in an operating mode (here called CAN) that is compatible with ISO 11898-2: 2016. In the data phase 452 of the frame 450 can the transceiver 12 , 32 can optionally be switched to another operating mode, which enables higher bit rates and thus fast data transmission.

The arbitration phase 451 is used to identify with the help of an identifier (ID) 451x bit by bit between the subscriber stations 10 , 20th , 30th negotiate which subscriber station 10 , 20th , 30th the message 45 , 46 with the highest priority and therefore for the next time to send at least in the subsequent data phase 452 exclusive access to the bus 40 of the bus system 100 gets. This is in the arbitration phase 451 the known CSMA / CR method is used, which allows simultaneous access by the subscriber stations 10 , 20th , 30th on the bus 40 allowed without the higher priority message 45 , 46 gets destroyed. This allows the bus system 100 relatively simple further bus subscriber stations 10 , 20th , 30th can be added, which is very beneficial.

Thus, in the arbitration phase 451 from the associated transmitting / receiving device 12 , 22nd , 32 a physical layer as used in CAN and CAN-FD. The physical layer corresponds to the bit transmission layer or layer 1 of the known OSI model (Open Systems Interconnection model).

Are the scheduling units 15th , 25th , 35 not activated, the frames 450 , 460 and the bus access of the individual subscriber stations is uncoordinated. Conflicts arise when communicating on the bus 40 resolved with an arbitration as defined in ISO 11898-1: 2015.

The CSMA / CR procedure has the consequence that there are so-called recessive states on the bus 40 must give which of other subscriber stations 10 , 20th , 30th with dominant states on the bus 40 can be overwritten. In the recessive state, prevail at the individual subscriber station 10 , 20th , 30th high-resistance conditions, which in combination with the parasites of the bus circuit results in longer time constants. This leads to a limitation of the maximum bit rate of today's CAN FD physical layer to currently around 2 megabits per second in real vehicle use.

A sender of the message 45 , 46 starts sending bits of the data phase 452 on the bus 40 only when the corresponding subscriber station 10 , 20th , 30th when the sender has won the arbitration and the subscriber station 10 , 20th , 30th as a sender, this gives exclusive access to the bus for sending 40 of the bus system 100 Has.

1. a) Übernahme und gegebenenfalls Anpassung bewährter Eigenschaften, die für die Robustheit und Anwenderfreundlichkeit von CAN und CAN FD verantwortlich sind, insbesondere Rahmenstruktur mit Identifizierer 451x und Arbitrierung nach dem CSMA/CR-Verfahren,
2. b) Steigerung der Netto-Datenübertragungsrate, insbesondere auf etwa 10 Megabit pro Sekunde,
3. c) Anheben der Größe der Nutzdaten pro Rahmen, insbesondere auf etwa 4kbyte.

In general, the following different properties can be implemented in the bus system with CAN XL compared to CAN or CAN FD:

1. a) Adoption and, if necessary, adaptation of proven properties that are responsible for the robustness and user-friendliness of CAN and CAN FD, in particular frame structure with identifier 451x and arbitration according to the CSMA / CR procedure,
2. b) Increase in the net data transmission rate, in particular to around 10 megabits per second,
3. c) Increase the size of the user data per frame, in particular to around 4kbytes.

3 shows a case for communication on the bus 40 , in which the scheduling units 15th , 25th , 35 are activated. In this case, each of the subscriber stations has deterministic bus access 10 , 20th , 30th possible. This is done when communicating on the bus 40 a transmission round or round C (cycle) is used, in which in the simplest case for each of the subscriber stations 10 , 20th , 30th a time slot S is present. The number SN of time slots S thus corresponds to the number N of subscriber stations 10 , 20th , 30th on the bus 40 . The bandwidth on the bus 40 is determined by the number N of subscriber stations 10 , 20th , 30th divided.

In the example of 3 there are four time slots S, namely the time slots S1 , S2 , S3 , S4 so that any four subscriber stations of the subscriber stations 10 , 20th , 30th available. Therefore any four subscriber stations become the subscriber stations 10 , 20th , 30th hereinafter referred to as subscriber stations 1, 2 , 3 , 4th designated.

In general, SN time slots S can be provided, SN being any natural number. The number of time slots S is in the example of 3 constant, i.e. the same in every round C. Alternatively, however, the number of time slots S can be varied.

There is at least one master user station on the bus 40 . The master subscriber station can be any subscriber station of the subscriber stations 10 . 20th , 30th be, ie the subscriber station is both master and normal subscriber. At the beginning of each round C, the master subscriber station sends a start frame which is referred to below as SOCR (start-of-cycle frame). In one embodiment, the SOCR is a frame with a high-priority identifier ID and a short data field DF. In particular, the data field DF can be used in the bus system 100 have a minimum length, in particular 0 bytes. All subscriber stations 1, 2 , 3 , 4th on the bus 40 synchronize with the SOCR and know when they are allowed to send something.

The scheduling units 15th , 25th , 35 cause the frame to be created 450 , 460 according to the following rules.

Any frame 450 , 460 starts again with an arbitration phase 451 . The identifier 451x can for any frame 450 , 460 can be selected as desired, as long as the usual rule for CAN is observed that every identifier 451x only exclusively from one of the subscriber stations 1, 2 , 3 , 4th is used.

The minimum time slot duration T_S_mn is at least one arbitration bit time, that is, as long as the bit time of a bit in the arbitration phase 451 . The maximum time slot duration T_S_mx is equal to the maximum length of a frame 460 or 450 . The minimum lap duration T_C_mn is thus equal to the sum of all minimum time slot durations T_S_mn plus the minimum duration of a SOCR. In addition, the maximum lap duration T_C_mx is equal to the sum of all maximum time slot durations T_S_mx plus the maximum duration of a SOCR.

Each subscriber station 1, 2 , 3 , 4th allowed on the bus 40 only in the time slot S1 , S2 , S3 , S4 send which for the subscriber stations 1, 2 , 3 , 4th is provided. In the present embodiment, each subscriber station 1, 2 , 3 , 4th in the time slot provided for them S1 , S2 , S3 , S4 a single frame 450 , 460 on the bus 40 send.

Each of the subscriber stations 1, 2 , 3 , 4th has in their time slot S1 , S2 , S3 , S4 a transmission opportunity TO (Transmit Opportunity). Thus the subscriber station 1, 2 , 3 , 4th in the time slot assigned to it S1 , S2 , S3 , S4 a frame 450 , 460 send or may miss the opportunity to send. After a minimum time slot duration T_S_mn, the transmission opportunity TO has expired.

In the example of 3 the minimum round duration T_C_mn is four arbitration bit times plus the duration of a SOCR because 4 time slots S1 , S2 , S3 , S4 for the four subscriber stations 1, 2 , 3 , 4th stand by. The minimum time slot duration T_S_mn is assumed to be the 1-arbitration bit time.

The following basic assumptions apply to the present exemplary embodiment. In the first round C, i.e. after switching on the bus system 100 , become the time slots S1 , S2 , S3 , S4 the individual subscriber stations 1, 2 , 3 , 4th assigned. The assignment takes place dynamically via the frame IDs or identifiers 451x which the subscriber stations 1, 2 , 3 , 4th to send their first frame 450 , 460 use. The transmission sequence is determined by means of the arbitration, which is the assignment of the time slots S1 , S2 , S3 , S4 to the subscriber stations 1, 2 , 3 , 4th corresponds.

If the subscriber stations 1, 2 , 3 , 4th are not switched on at the same time, is the allocation of the time slots S1 , S2 , S3 , S4 only completed when the last subscriber station 1, 2 , 3 , 4th is switched on and if each subscriber station 1, 2 , 3 , 4th a frame 450 , 460 sent. The allocation of the time slots remains in the subsequent rounds C S1 , S2 , S3 , S4 to the subscriber stations 1, 2 , 3 , 4th receive. This means that there is no new arbitration and the sending order is unchanged. If one or more of the subscriber stations 1, 2 , 3 , 4th go to sleep and wake up again, a re-integration takes place with the help of the SOCR, which specifies the beginning of each round C. This is later also based on 4th described in more detail. If a subscriber station has forgotten its time slot assignment, it can also integrate itself as when it was first switched on, which is subsequently based on 3 is described. The sending sequence is determined by the frame identifier used 451x and through arbitration on the bus 40 certainly.

When communicating on the bus 40 applies that the SOCR is distinguishable from other frameworks. This can be done, for example, by using a special frame identifier 451x happen. In particular, the frame identifier has 451x the highest priority and thus the corresponding priority ID. This frame identifier 451x must then all subscriber stations 1, 2 , 3 , 4th on the bus 40 be known. Alternatively, this can also be done, for example, by a special value in the data type field DT in the frame that is received from all subscriber stations 1, 2 , 3 , 4th on the bus 40 is evaluated accordingly. Alternatively or additionally, a predetermined bit can be used in the frame in order to transport the information that this frame is a SOCR. Then, for example, the value 0 = no SOCR and the value 1 = SOCR for this predetermined bit. Alternatively or additionally, it is conceivable to use a bit or byte in the data field DF to identify the SOCR.

It is possible that the SOCR has a different amount of information in its data field DF. In the present exemplary embodiment, no information is contained in the data field DF of the SOCR. Thus, in this variant, no further information than the start of the next round C is sent to the subscriber stations 1, 2 , 3 , 4th communicated. This has the advantage that the SOCR uses as little communication bandwidth as possible.

3 shows a starting round C_SU in which the time slots are assigned in a time period T_C_SU S1 , S2 , S3 , S4 to the subscriber stations 1, 2 , 3 , 4th is determined. As mentioned before, every round C starts with a SOCR. Receives one of the subscriber stations 1, 2 , 3 , 4th the SOCR, this subscriber station is 1, 2 , 3 , 4th ready one of the time slots S1 to S4 to be released for sending, as described in more detail below. The time slot in which the SOCR is sent / received corresponds to a time slot “S0”. For the sake of simplicity, the example of 3 assumed that all subscriber stations 1, 2 , 3 , 4th a frame right at the beginning 450 , 460 want to send.

In the time slot S1 start all subscriber stations 1, 2 , 3 , 4th simultaneously a frame and participate in the bus arbitration, as indicated by A1234 in 3 shown. The participant station 4th wins arbitration A and sends its frame. This is with TX4 in 3 shown, where TX4 for the transmission signal TX of the subscriber station 4th and the frame is based on the transmit signal TX4. This is the time slot S1 the subscriber station 4th assigned.

In the time slot S2 start the subscriber stations 1, 2 , 3 simultaneously a frame and participate in the bus arbitration, as indicated by A123 in 3 shown. The participant station 2 wins the arbitration and sends its frame. This is with TX2 in 3 shown. This is the time slot S2 the subscriber station 2 assigned.

For time slot S3 an arbitration between the subscriber stations 1, 3 performed as previously described. Ultimately, in the example of 3 the time slot S3 assigned to the subscriber station 1.

The time slot S4 becomes the subscriber station 3 assigned. Arbitration no longer takes place because the other subscriber stations 1, 2 , 4th in the time slot S4 send nothing.

Therefore, the TX transmission order is determined by the arbitration in the following as TX_4_2_1_3.

Normal operation of the bus system can then be achieved 100 begin. A possible lap C in operation could be a lap C_B that takes place in 3 is shown in the right part of the figure. In round C_B, the TX transmission sequence remains unchanged as TX_4_2_1_3. In round C_B, the subscriber stations transmit 3 , 4th . In contrast, the subscriber stations 1, 2 Not. Therefore, the subscriber stations use 3 , 4th your opportunity to broadcast TO. The subscriber stations 1, 2 let their transmission opportunity TO pass, however. This results in an average lap duration T_C_B. The maximum lap duration T_C_mx results when in each time slot S1 to S4 from the associated subscriber station 1, 2 , 3 , 4th a frame 450 , 460 is sent with the maximum length. The number 1 in the time slot S3 expresses that this time slot is assigned to subscriber station 1. The number 2 in time slot S2 expresses that this time slot of the subscriber station 2 assigned. This applies analogously to the time slots S1 and S4 and the subscriber stations 3 , 4

To implement the previously described timing for sending frames 450 , 460 on the bus 40 is each of the scheduling units 15th , 25th , 35 constructed as described below.

Each master subscriber station 1, 2 , 3 , 4th on the bus 40 knows the number SN of time slots S1 , S2 , S3 , S4 per round C. In the simplest case, the number of participant stations is 1, 2 , 3 , 4th on the bus 40 the number of time slots S1 , S2 , S3 , S4 per round C, so that there is a 1: 1 assignment of time slots and subscriber stations. The number SN of time slots S1 , S2 , S3 , S4 per lap C is in the scheduling units 15th , 25th , 35 the at least one master subscriber station stored.

In general, any subscriber station in the bus system 100 can take over the functions of the master subscriber station described above and below. Thus the master subscriber station and a normal subscriber station are not two separate subscriber stations. One subscriber station can thus take on both functions, for example the subscriber station 1 could also be the master subscriber station.

Normal operation begins for one Subscriber station 1, 2 , 3 , 4th as soon as subscriber station 1, 2 , 3 , 4th knows which time slot number is assigned to it. This is according to 3 the case if the subscriber station 1, 2 , 3 , 4th sent her first frame. Since each round C begins with a SOCR, the master subscriber station sets the count value Scnt of the counting module 15th , 25th , 35 your scheduling unit 15th , 25th , 35 after sending the SOCR to Scnt: = 1. In addition, each subscriber station sets 1, 2 , 3 , 4th the count value Scnt of the counting module 15th , 25th , 35 your scheduling unit 15th , 25th , 35 after receiving the SOCR on Scnt: = 1. From now on the counting module counts 151 , 251 , 351 with at least one counter the number of frames received 450 , 460 on the bus 40 and the number of elapsed transmission opportunities TO. The counting module counts here 151 , 251 , 351 per received frame 450 , 460 and per elapsed transmission opportunity TO, so that the count value Scnt of the at least one counter is incremented by 1 in each case, and Scnt: = Scnt + 1.

As soon as the frame start bit (start of frame bit) of a frame 450 , 460 on the bus 40 is sent, the counting module evaluates 151 , 251 , 351 the frame 450 , 460 as a sent frame 450 , 460 on the bus 40 . This also applies if the transmission is aborted by the sender, for example due to an error frame 47 because of a mistake.

Applies in the counting module 151 , 251 , 351 of a subscriber station for the count value Scnt == own time slot number, the next time slot is its own time slot. Thus the subscriber station 1, 2 , 3 , 4th after the count value Scnt == own time slot number in the next time slot the own transmission opportunity TO. Now the affected subscriber station 1, 2 , 3 , 4th a frame 450 , 460 send or let the transmission opportunity TO pass. The master subscriber station counts with its counting module 151 , 251 , 351 from 1 to SN. The simple subscriber stations count with their counting module 151 , 251 , 351 from 1 to “own time slot number”, then the simple subscriber stations, more precisely their counting module 151 , 251 , 351 keep counting or not.

Applies in the counting module 151 , 251 , 351 a master subscriber station for the count value Scnt == SN, the next time slot is that time slot in which the SOCR must be sent. Now the master subscriber station 1, 2 , 3 , 4th a SOCR framework 450 , 460 send. If there are several masters, all master subscriber stations start sending the SOCR in this time slot. The SOCR with the highest priority will prevail through arbitration.

The scheduling unit also remembers it 15th , 25th , 35 a subscriber station 1, 2 , 3 , 4th the count value Scnt as its own time slot number if the subscriber station 1, 2 , 3 , 4th could send a frame. If it lets its transmission opportunity TO elapse, it keeps its own time slot number from the last round C.

This is necessary when the order of transmission on the bus 40 is reassigned and this leads to arbitration again. This can be the case if one of the subscriber stations 1, 2 , 3 , 4th was woken up again and this then wants to participate in the bus communication again. This is based on 4th described in more detail below.

After switching on or waking up, subscriber stations 1 2 , 3 , 4th unknown which of the time slots S1 , S2 , S3 , S4 per round C of the respective participant station 1, 2 , 3 , 4th assigned.

4th shows the case that the subscriber station 3 first slept and then woke up again. The following description also applies if several subscriber stations are switched on again and try to reintegrate at the same time.

For example, is the subscriber station 3 at time t1 in 4th woke up again and ready to send. Up to this point in time and thus also up to the point in time before the subscriber station 3 was put to sleep, the sending order was set as TX_1_2_3_4, as shown on the left in 4th with the numbers shown in the time slots. The subscriber station then waits 3 until it receives the SOCR. Since the subscriber station 3 has forgotten its own time slot number, the subscriber station tries 3 to send a frame after receiving the SOCR, ie from time t2. Because the time slot S1 however, the subscriber station 1 is assigned and this also tries to send its frame, this leads to an arbitration on the bus 40 .

In the example of 4th therefore takes place in a time slot S1 an arbitration between the frames of the subscriber stations 1, 3 instead of, as with A13 in 4th shown. In the example of 4th wins the frame of subscriber station 1 the arbitration, so that ultimately the transmission signal TX1 of subscriber station 1 in the time slot S1 is sent and the subscriber station 1 its time slot S1 retains.

As the framework of the subscriber station 3 has lost the arbitration, the subscriber station repeats 3 sending your frame until the frame has won the arbitration and the subscriber station 3 can send its frame or aborts the attempt to send due to a bus error. Each subscriber station 1, 2 , 3 , 4th can send a frame in a round C.

The frames of the subscriber stations therefore arbitrate 2 , 3 in the time slot S2 as with A23 in 4th shown. In the example of 4th wins the frame of the participant station 2 the arbitration, so that ultimately the transmission signal TX2 of the subscriber station 2 in the time slot S2 is sent. The subscriber station thus retains 2 also their time slot S2 .

In the next time slot S3 only tries the subscriber station 3 to send their frame. The other subscriber stations 1, 2 , 4th send in the time slot S3 not because the time slot S3 previously the subscriber station 3 was assigned. In the time slot S3 therefore there is no arbitration. This allows the subscriber station 3 send their frame and has their time slot S3 found again.

Then can also for the subscriber station 3 start normal operation again, since the subscriber station 1, 2 , 3 , 4th again knows which time slot S1 , S2 , S3 S4 it is assigned, ie which is its own time slot number.

The frame identifier 451x can for any frame 450 , 460 can be selected as desired, as long as the usual rule for CAN is observed that every identifier 451x only exclusively from a subscriber station 1, 2 , 3 , 4th is used. However, it is alternatively conceivable that each subscriber station 1, 2 , 3 , 4th only a single identifier to send all of their frames 451x used.

Deviating from the example of 4th the following applies. Had the participant station 3 a higher priority frame identifier 451x used as the subscriber station 1, the subscriber station would have 3 their frame already in the time slot S1 can send. This would have the subscriber station 3 the time slot S1 taken over by the subscriber station 1. In this case, the subscriber station 1 would then have its frame in the time slot at the latest S3 can send because in the time slot S3 then no other subscriber stations 2 , 3 , 4th would send.

As a result, depending on the result of the arbitration, the assignment of the time slots S1 , S2 , S3 , S4 be redistributed.

One advantage of this exemplary embodiment is that the implementation is very uncomplicated to configure. In the simplest case, in which each subscriber station 1, 2 , 3 , 4th exactly one time slot S1 , S2 , S3 , S4 is assigned, the bus system comes 100 for the described communication with the scheduling units 15th , 25th , 35 without configuration. It is sufficient that only the master user station has the number N of user stations on the bus 40 and thus knows the number SN.

Another advantage of the present exemplary embodiment is that communication on the bus 40 is self-organizing through the arbitration, since the allocation of the time slots S1 , S2 , S3 , S4 to the subscriber stations 1, 2 , 3 , 4th takes place dynamically via the arbitration.

The time delay in the worst case (worst-case delay) for the bus access of a subscriber station 1, 2 , 3 , 4th is roughly like the PLCA of 10BASE-T1S, namely 2 * SN maximum frame length plus the frame length of the SOCR.

In addition, the present embodiment has the following advantage in particular. Is it due to an error in one of the scheduling units 15th , 25th , 35 to the fact that a subscriber station sends in the wrong time slot, this only leads to arbitration and a possible delay in sending. However, such an error cannot destroy the two frames on the bus, which can lead to data loss.

According to a modification of the first exemplary embodiment, at least one backup master is provided. This also gives in case on the bus 40 at least one master subscriber station that regularly sends the SOCR. The backup master also uses a fixed frame identifier for the SOCR 451x . This means that there can be no “single point of failure” at which there is no longer a master subscriber station. The at least one backup master can be from one of the subscriber stations 10 , 20th , 30th of the bus system 100 be realized.

Each backup master uses a predetermined frame identifier for the SOCR it sends 451x . Ideally the frame identifiers have 451x the backup master has a lower priority than the frame identifier 451x the master subscriber station.

If the master subscriber station fails, there are two ways in which the at least one backup master can step in.

According to a first variant, the master subscriber station and all backup masters always start the SOCR at the same time. Since the master subscriber station and all backup masters have different frame identifiers 451x use and da the frame identifier 451x the master subscriber station has the highest priority, the master subscriber station wins the arbitration. The backup masters recognize this and make no further SOCR transmission attempt in this round C. Each subscriber station 1, 2 , 3 , 4th on the bus 40 recognizes due to the frame identifier 451x which master sent the SOCR.

According to a second variant, the backup masters check whether the intended master is sending the SOCR or not sending as expected. "Not sending" is recognized by the backup masters after a predetermined waiting period (time-out) has elapsed. For example, the predetermined waiting time (time-out) is an arbitration bit time. The backup master jumps in after the predetermined waiting time (time-out) and sends its SOCR so that the "single point of failure" can be avoided.

5 shows a timing in the bus system 100 to illustrate a communication according to a second embodiment.

In contrast to the timing of the communication according to the previous exemplary embodiment, in the present exemplary embodiment the own time slot number is already firmly specified. This is achieved by being on the bus 40 permanently assigned time slot numbers are used. As a result, a reintegration process is superfluous in the present exemplary embodiment, since each subscriber station 1, 2 , 3 , 4th , the bus 40 the time slot assigned to it S1 , S2 , S3 , S4 knows.

The time slots can be assigned implicitly, for example, time slot 1 is assigned to subscriber station 1, the subscriber station 2 is the time slot 2 assigned, etc., as in 5 shown as an example.

Alternatively, the time slots can be assigned explicitly, in particular communicated in the SOCR.

If the assignment is made explicitly with the SOCR, information is transmitted in the data field DF of the SOCR. It is possible here for the number SN of time slots and the time slot assignment to the subscriber stations of the bus to be in the data field DF of the SOCR 40 is included. Accordingly, with the data field DF of the SOCR to the subscriber stations 1, 2 , 3 , 4th communicated the number SN of the time slots in the now following round as well as the assignment of the time slots to the subscriber stations of the bus 40 communicated. In this case, there is the option that in each round C the number SN of time slots and the time slot assignment to the subscriber stations of the bus 40 can be set arbitrarily and thus can be different in each round C.

For example, the first byte in the data field DF of the SOCR contains the number SN of time slots in the round that is now beginning. In addition, the assignment of the time slots to the subscriber stations of the bus can be done in the following bytes in the data field DF of the SOCR 40 be included. For example, after byte 0, byte 1 in data field DF contains the allocation of time slots S1 to a subscriber station number, byte 2 the allocation of time slot S2 to a subscriber station number, etc.

This allows the bandwidth, i.e. the number and / or the length of time slots S1 , S2 , S3 , S4 that a subscriber station 1, 2 , 3 , 4th of the bus 40 is guaranteed, can be easily increased or decreased during operation. This results in the length of the time slots S1 , S2 , S3 , S4 by the length of the at least one frame sent. For example, it is possible to switch to a special operating mode, in particular flashing in the workshop, where the transmitter is granted a particularly high bandwidth. Alternatively or in addition, a security emergency can be responded to. One such emergency could be a component failure. Under such a condition, at least one rather unimportant subscriber station could be completely or at least partially prohibited from communication. This means that additional frames can be allocated bandwidth.

By evaluating the information on the assignment of the time slots S1 , S2 , S3 , S4 , for example from the bus 40 received SOCR is for the respective subscriber station 1, 2 , 3 , 4th of the bus 40 the assignment of the time slots S1 , S2 , S3 , S4 visible in round C. Therefore, the procedure is as follows.

In operation of the bus 40 according to 5 every subscriber station knows 1, 2 , 3 , 4th on the bus 40 , more specifically, each scheduling unit 151 , 251 , 351 that a new round C always begins with a SOCR. Each subscriber station 1, 2 , 3 , 4th on the bus 40 , more specifically, each scheduling unit 151 , 251 , 351 , knows which time slot S1 , S2 , S3 , S4 is assigned to the subscriber station. Each subscriber station 1 thus knows 2 , 3 , 4th on the bus 40 , more specifically, each scheduling unit 151 , 251 , 351 in which time slot S1 , S2 , S3 , S4 the subscriber station is allowed to send.

By having the time slots S1 , S2 , S3 , S4 the subscriber stations S1 , S2 , S3 , S4 are already assigned and each subscriber station 1, 2 , 3 , 4th always only in their time slot S1 , S2 , S3 , S4 no arbitration takes place. This means that there is no need to differentiate between the two cases “re-integration after switching on” and “normal operation”. There is only normal operation that is already in With reference to the first embodiment is described.

According to 5 subscriber station 1 is the time slot S1 assigned to the subscriber station 2 is the time slot S2 assigned to the subscriber station 3 is the time slot S3 assigned and the subscriber station 4th is the time slot S4 assigned. This is on the left of 5 illustrated. The assignment is made, for example, by configuring the scheduling unit.

In the example of 5 becomes the subscriber station 3 switched on and is ready at time t4 to participate in the CAN communication. The subscriber station then waits 3 for example on the SOCR. The subscriber station is on receipt of the SOCR 3 synchronized. The subscriber station then waits 3 to the time slot assigned to it, i.e. in the example of 5 on the time slot S3 . The participant station 3 can then send its frame from a point in time t5.

In the second exemplary embodiment, the subscriber station number is thus obtained from the system integrator or from the configurator of the bus system 100 given. Hence the order of communication on the bus 40 no longer self-organizing, but rather it is specified, namely via the assignment of the subscriber station number and optionally also via the information in the SOCR. The subscriber stations are then only allowed to send in a defined order.
This embodiment variant is also more robust with regard to the counting of the time slots, since the allocation of the time slots is already fixed. In addition, the third present embodiment also has the aforementioned advantage that no frame is destroyed if it is caused by an error in one of the scheduling units 15th , 25th , 35 in addition, a subscriber station sends in the wrong time slot. Such an error only leads to an arbitration but not to the destruction of the two frames on the bus.

6 shows a timing in the bus system 100 to illustrate a communication according to a third embodiment.

In contrast to the timing of the communication according to the previous embodiment, it is also possible in the present embodiment that a subscriber station 1, 2 , 3 , 4th after switching on or waking up is synchronized again to the time slot number even more quickly than in the previous exemplary embodiments.

Therefore, in the present embodiment, a subscriber station number is used as additional information in the frame 450 , 460 transfer. This is on the bus 40 or by evaluating the from the bus 40 received frame visible which subscriber station 1, 2 , 3 , 4th of the bus 40 is currently sending. So for each subscriber station 1, 2 , 3 , 4th known which subscriber station 1, 2 , 3 , 4th is currently sending and thus which number the current time slot is S1 , S2 , S3 , S4 Has. The procedure for this in the present exemplary embodiment is as follows.

The subscriber station number can be found in various places in the frame 450 , 460 be transmitted. For example, the priority ID can be the same as the frame identifier 451x is the subscriber station number of subscriber station 1, 2 , 3 , 4th correspond. Alternatively or additionally, the subscriber station number can be transmitted in the data field DF or with via the data type field (DataType field) DT.

In the example of 6 is the allocation of the time slots S1 , S2 , S3 , S4 to the subscriber stations 1, 2 , 3 , 4th to the left of 6 to see. The time slot S1 is assigned to subscriber station 1, etc. and the time slot S4 is the subscriber station 4th assigned.

The participant station 3 is switched on and is in the example of 6 ready at time t6 to take part in the CAN communication. The subscriber station then waits 3 on the SOCR or on another frame in order to synchronize to the time slot numbers. At time t7, the subscriber station has 3 a frame from the subscriber station 2 received as soon as the subscriber station 3 those in the context of the subscriber station 2 has received transmitted subscriber station number, the subscriber station knows 3 that the time slot just elapsed is the time slot S2 is. This is the subscriber station 3 synchronized to the time slot numbers. In this example, the time slot directly follows S3 comes, the subscriber station can in the time slot S3 send their frame with the transmit signal TX3. Had the participant station 2 the subscriber station would have let its transmission opportunity TO elapse 3 received the SOCR a few bits later and would thus also be synchronized to the time slots S.

It is very advantageous in the third exemplary embodiment that a subscriber station 1, which is switched on or woken up again, 2 , 3 , 4th due to the time slot S1 , S2 , S3 , S4 transmitted subscriber station number faster to the permanently assigned time slot numbers S1 , S2 , S3 , S4 or in communication on the bus 40 existing time slot numbers S1 , S2 , S3 , S4 is synchronized than in the previous embodiments. Thus, the time delay in worst case delay for bus access of a subscriber station 1, 2 , 3 , 4th reduced to 1 * SN maximum frame length plus the frame length of the SOCR. In the worst case, the time delay is thus approximately half less than in the previous exemplary embodiments.

This embodiment variant is also more robust with regard to the counting of the time slots since the time slot number is on the bus 40 you can see. In addition, the present exemplary embodiment also has, in particular, the previously mentioned advantage that no frame is destroyed if it is caused by an error in one of the scheduling units 15th , 25th , 35 in addition, a subscriber station sends in the wrong time slot. Such an error only leads to arbitration but not to the destruction of the two frames on the bus.

7th shows a timing in the bus system 100 to illustrate a communication according to a fourth embodiment. For this shows 7th in its left part a lap with a minimum lap duration T_C_mn, in which all time slots S1 to S4 each have at least two arbitration bit times. For example, the time slot has S3 a first bit time B1_S3 and a second bit time B2_S3 . The same applies to the other time slots S1 , S2 , S4 .

A subscriber station 1, 2 , 3 , 4th that are in a time slot S1 , S2 , S3 , S4 its transmission opportunity TO has its frame in the first bit of the time slot assigned to it S1 , S2 , S3 , S4 start to be able to send a frame guaranteed. Thus elapses in the time slot S1 , S2 , S3 , S4 not a bit. If a subscriber station 1, 2 , 3 , 4th the first bit of their time slot S1 , S2 , S3 , S4 elapse, subscriber station 1 has 2 , 3 , 4th also let their transmission opportunity TO pass that the subscriber station 1, 2 , 3 , 4th would have guaranteed the dispatch of a cream. Thus subscriber station 1 would like to 2 , 3 , 4th currently not sending a frame.

As a result, another subscriber station 1, 2 , 3 , 4th now this time slot S1 , S2 , S3 , S4 use to send. However, it is possible, for example, for the subscriber station 1 to have its first bit time B1_S1 of their time slot S1 passes, but then in the second bit time B2_S1 of their time slot S1 but starts with sending a frame. In this example, all subscriber stations 1, 2 , 3 , 4th in the second bit B2_S1 of the time slot S1 start a frame. The frames can also be around this free time slot S1 "Fight", so on the bus 40 arbitrate. So that the frame that has the highest priority wins the arbitration, the subscriber stations 1, 2 , 3 , 4th for their frames which start in the second bit of a time slot, identifiers 451x that match the priority of the frame. As a result of the arbitration, the frame with the highest priority will prevail.

This configuration of the minimum duration T_S_mn of the time slots S1 to S4 it is possible that one of the subscriber stations 1, 2 , 3 , 4th uses the transmission opportunity TO of another subscriber station because it is clear from an unused first bit time that the corresponding subscriber station has not used its guaranteed transmission opportunity TO.

In the example of 7th uses the subscriber station 4th the fourth time slot assigned to it S4 for sending the transmission signal TX4 in one frame. At a time t8 during the time slot S4 is the subscriber station 3 ready to send a frame. Since the subscriber station 1 does not send a frame - the first bit time B1_S1 elapses unused - sends the subscriber station 3 from time t9 the transmission signal TX3 as a frame in the second bit time B2_S1 of the time slot S1 . The second and third time slot S2 , S3 is in each case from the associated subscriber station 2 , 3 used. Thus, the transmit signals TX2, TX3 are each in a frame on the bus 40 Posted. Since the subscriber station 4th no frame is sent - the first bit time B1_S4 elapses unused - the subscriber stations send 1, 2 from time t10 frame on the bus 40 . In the following arbitration, the subscriber station wins 2 so that the transmission signal TX2 as a frame in the time slot S4 on the bus 40 is sent.

One advantage of the present exemplary embodiment is that a deterministic allocation of the communication bandwidth can be mixed with data traffic with the best effort (best effort data traffic). The data traffic with the best effort only comes about if some subscriber stations 1, 2 , 3 , 4th the bandwidth allocated to them, i.e. the transmission slot S1 , S2 , S3 , S4 , not use.

Another major advantage of the present exemplary embodiment is that the time delay in the worst case (worst-case delay) for bus access increases only minimally as a result. The time delay increases minimally because the subscriber stations first wait a bit before using another time slot.

In principle, the minimum time slot duration T_S_mn can alternatively be three or more arbitration bit times. The subscriber stations 1, 2 , 3 , 4th on the bus 40 can then be divided into different priority classes. The lower the priority class of a subscriber station 1, 2 , 3 , 4th , the later within a free time slot the subscriber station 1, 2 , 3 , 4th start a broadcast.

According to a modification of the present exemplary embodiment, the configuration with at least two bit times can be used for subscriber stations 1, 2 , 3 , 4th after waking up or switching on, re-integrate in such a way that a sending subscriber station 1, 2 , 3 , 4th is not disadvantaged by the sending subscriber station 1, 2 , 3 , 4th the time slot assigned to it S1 , S2 , S3 , S4 is taken away. For this purpose, each subscriber station 1 uses, if possible, 2 , 3 , 4th only time slots for re-integration S1 , S2 , S3 , S4 which were not used in the first bit by the actual timeslot holder. If the re-integrating subscriber station of the subscriber stations 1 sends 2 , 3 , 4th from the second bit of the time slot S1 , S2 , S3 , S4 its frame and wins the arbitration and can send the frame successfully, that is, error-free, so the time slot is then assigned to it.

8th shows a timing in the bus system 100 to illustrate a communication according to a fifth embodiment.

In contrast to the previous exemplary embodiments, the communication bandwidth is on the bus 40 in the present exemplary embodiment not evenly between the subscriber station 1, 2 , 3 , 4th distributed. Instead, a so-called WRR method (Weighted Round Robin method) is used in the present exemplary embodiment. Each subscriber station receives 1, 2 , 3 , 4th a further parameter W (weight = weight), which is in the associated scheduling unit 15th , 25th , 35 can be set during configuration. The parameter W gives the number of frames 450 , 460 which subscriber station 1, 2 , 3 , 4th per lap C. A subscriber station 1, 2 , 3 , 4th W timeslots are made available for this purpose. The parameter SN set in the at least one master subscriber station therefore no longer corresponds to the number of subscriber stations 1, 2 , 3 , 4th , but the sum of all values of the parameter W.

8th shows an example with four subscriber stations 1, 2 , 3 , 4th for which the parameter W = 2 is set for subscriber station 1. Against this is for the other subscriber stations 2 , 3 , 4th one parameter W = 1 is set in each case. The number SN of time slots is thus calculated as SN = 2 + 1 + 1 + 1 = 5. As a result, a round C has a number of 5 time slots, namely S1 , S2 , S3 , S4 , S5 . Here the subscriber station 1 can have two frames per round 450 , 460 send, namely in the time slots S1 and S2 . The other participant stations 2 , 3 , 4th can only have one frame per round C. 450 , 460 send.

9 shows, to explain a sixth exemplary embodiment, a differential voltage V-diff, which results from the difference between the bus signals CAN_H and CAN_L on the bus 40 calculated.

According to 9 sends a subscriber station 1, 2 , 3 who do not use their transmission opportunity TO put a short dominant pulse P at the beginning of the bits B1_S1 , B1_S2 , B1_S3 , etc. in their time slot S1 , S2 , S3 . In the example of 9 is in every time slot S1 , S2 , S3 only one bit, namely the bit B1 sent, since the minimum time slot duration T_S_mn is assumed here with an arbitration bit time. The bits are used by the receiving subscriber stations 1, 2 , 3 sampled at a sampling time t_A. If the minimum duration T_S_mn of a time slot corresponds to several arbitration bit times, then the subscriber station to which the time slot is assigned can send a dominant pulse P at the beginning of each bit if the subscriber station lets its transmission opportunity TO elapse.

The associated subscriber station sends 1, 2 , 3 in the recessive bits of your time slot S1 , S2 , S3 a dominant pulse P of eg 200 ns. All CAN subscriber stations 1, 2 , 3 synchronize to the recessive-dominant edge S_F of the dominant pulse P. Since the arbitration bit time is limited to 1000 ns or 1 Mbit / s according to the aforementioned specification, a corresponding pulse P of 200 ns is not restrictive. All subscriber stations 1, 2 , 3 feel the actually recessive bit B1 despite the dominant pulse P, it turns into recessive because the pulse P has long ended again at the sampling time t_A.

This makes it possible for the subscriber stations 1, 2 , 3 the synchronization to the time slots S1 , S2 , S3 not lose, even when in communication on the bus 40 long idle phases occur in which all subscriber stations 1, 2 , 3 do not use their transmission opportunity TO. By means of the dominant pulses P, the subscriber stations 1, 2 , 3 are kept synchronized.

So comes the bus system 100 coped with clocks that have relatively high tolerances. The subscriber stations 1 synchronize here, 2 , 3 on recessive dominant flanks on the bus 40 .

According to a seventh embodiment, it is possible that one or more subscriber stations 1, 2 , 3 , 4th of the previous embodiments several frames per time slot S1 , S2 , S3 , S4 send. This configuration is advantageous, for example, in order to increase the communication bandwidth on the bus 40 to divide more equitably if, for example, the subscriber station 1 typically short frames 460 sends and the subscriber station 2 typically long frames 450 sends. Can each subscriber station 1, 2 only ever one frame in the time slot assigned to it S1 , S2 send, then the subscriber station has 1 in the process according to the first to third exemplary embodiment, less bandwidth than the subscriber station 2 .

In order to achieve more fairness with regard to the communication bandwidth than in the first to third exemplary embodiments, the subscriber station 1 is permitted, for example, during its time slot S1 several short frames 450 to send. To be fair, the framework should 450 in total no longer than a frame 450 maximum length.

The signaling that the subscriber station 1 still has a frame 460 TO is sent on this transmission opportunity can be done in the following ways.

For example, the identifier 451x be used. The lower 4 bits of the identifier (ID) 451x used to identify the subscriber station 1. The next 7 bits of the identifier (ID) 451x are used to indicate that there are other frames 460 will follow. For example, 0x14 can signal that the subscriber station 4th sends a frame, the 1 signaling that the frame is followed by further frames. Then 0x04 could signal that the subscriber station 4th sends a frame, the 0 indicating that the frame is not followed by any frames.

According to another possibility of signaling that the subscriber station 1 still has a frame 450 When TO is sent on this transmission opportunity, there is a Data Type (DT) field in the header of the frame 450 usable. For example, DT = 0x30 can signal that no other frame is following the same subscriber station. DT = 0x31 could therefore signal that another frame is following the same subscriber station.

Alternatively, according to yet another possibility of signaling, there is a dedicated bit in the header of the frame 460 usable.

Alternatively, a bit or byte at the beginning of the in 2 shown data field DF in the data phase 452 usable.

The advantage is that more fairness with regard to the division of the communication bandwidth between subscriber stations 1, 2 , 3 , 4th can be produced in the case in which the subscriber stations 1, 2 , 3 , 4th frames of different lengths 450 , 460 to ship.

According to an eighth exemplary embodiment, it is possible that in the time planning units 15th , 25th , 35 the number SN of time slots is set greater than the number N of subscriber stations. In this case, there is at least one time slot left that is not shared by any of the subscriber stations and thus not for anyone on the bus 40 heard. If this is combined with the fourth exemplary embodiment, where it is explained how other subscriber stations can use unused time slots, the surplus time slots can be used by each subscriber station.

Since, in principle, all subscriber stations can transmit simultaneously in the excess time slots and thus around the bus 40 arbitrate, this corresponds to strict priority scheduling.

For example, the bus has N = 4 subscriber stations, i.e. subscriber stations 1, 2 , 3 , 4th , and SN = 5 time slots, i.e. the time slots S1 , S2 , S3 , S4 , S5 . A time slot is exclusively allocated to each subscriber station. There in time slot S5 a node will never send immediately, the nodes can start from the second bit of the time slot around the time slot S5 arbitrate.

Alternatively, this eighth exemplary embodiment can also be designed as an extension of the second or third exemplary embodiment. The scheduling units 15th , 25th , 35 have configured not only the number SN of time slots, but also the number of time slots that are available to all subscriber stations, for example at the end of round C. If the time slots are permanently assigned to the subscriber stations, as in the second and third exemplary embodiments, the time slot number is optionally contained in the transmitted frame and a SOCR marks the start of a round C, then a time planning unit is able to determine the time slot S5 (from the example above). If the time slot S5 has come, all subscriber stations around the bus can simply be here 40 arbitrate. The combination with the fourth exemplary embodiment is no longer absolutely necessary.

Since each of the subscriber stations 1, 2 , 3 , 4th in the time slot S5 can transmit, the transmission opportunity TO is allocated in the time slot S5 strictly according to the priority, i.e. the identifier 451x the frame that the subscriber stations 1, 2 , 3 , 4th in the time slot S5 send (Strict Priority Scheduling). The frame identifier 451x the news 450 , 460 is in this time slot S5 sensibly to choose according to the actual priority of the messages so that the frame with the highest priority can prevail.

According to a ninth embodiment, it is possible that the arbitration phase 451 is completely or at least partially omitted from communication. This takes place in the normal Operation, also in the first exemplary embodiment, with deterministic time planning (scheduling) with the time planning units 15th , 25th , 35 no arbitration because each subscriber station 1, 2 , 3 , 4th one or more time slots S1 , S2 , S3 , S4 are allocated. As a result, after the time slots have been assigned S1 , S2 , S3 , S4 or in this operating point, the arbitration phase 451 before and after the data phase 452 be completely or at least partially omitted.

This is the arbitration phase 451 now shorter than with CAN, i.e. shorter than currently specified in ISO 11898-1: 2015.

In such a case, there are the following two modes of operation. In a first operating mode, all subscriber stations use 1, 2 , 3 , 4th normal CAN frames or CAN XL frames when switched on, because arbitration can occur on the bus. As soon as all subscriber stations 1, 2 , 3 , 4th are in operation and all subscriber stations 1, 2 , 3 , 4th on the time slots S1 , S2 , S3 , S4 are synchronized, there is therefore no more arbitration. It is therefore possible to switch to the second operating mode, in which the arbitration phase 451 is completely or at least partially omitted.

This can avoid the arbitration phase 451 and the frame end phase 453 with their relatively long bits that come before and after the data phase 452 are arranged to a relevant overhead during data transmission on the bus 40 and thus leads to a lower net data rate.

According to a tenth exemplary embodiment, it is possible that the identifiers 451x that is used to send the frame 450 , 460 used, can be divided into two areas. First in a high priority area that is for those frames 450 , 460 is used, which is sent by a subscriber station in the time slot assigned to the subscriber station. And secondly, in a low-priority area that is used for those frames that are sent in a time slot that is not exclusively assigned to the sending subscriber station.

In order to try to use a time slot that is exclusively assigned to another subscriber station, subscriber station 1, for example, the currently present time slot, must S3 is not assigned exclusively, simply when attempting to send the frame 450 , 460 an identifier 451x use from the lower priority area. This ensures that, for example, the subscriber station 3 , which in this example is the currently present time slot S3 is assigned exclusively, the arbitration would always win and thus this time slot S3 the subscriber station 3 remains exclusively assigned. However, if in this example at least one of the other subscriber station 1, 2 , 4th has to send something, this other subscriber station 1, 2 , 4th right at the beginning of the time slot S3 try a framework 450 , 460 with an identifier 451x to send from the lower priority area.

This has the advantage that in the present embodiment the minimum time slot duration T_S_mn remains at one arbitration bit time, whereas in the fourth embodiment the minimum time slot duration T_S_mn is two arbitration bit times.

All previously described configurations of the subscriber stations 1, 2 , 3 , 4th , 10 , 20th , 30th , the bus system 100 and the methods detailed therein can be used individually or in all possible combinations. In particular, all features of the exemplary embodiments described above and / or their modifications can be combined as desired. Additionally or alternatively, the following modifications in particular are conceivable.

Even if the invention is described above using the example of the CAN bus system, the invention can be used in any communication network and / or communication method. In particular, two different communication phases can be used in the communication network and / or communication method, as before with regard to the communication phases 451 , 452 described.

In particular, the bus system 100 According to the exemplary embodiments, it can be a communication network in which data can be transmitted serially at two different bit rates. It is advantageous, but not a mandatory requirement, that in the bus system 100 an exclusive, collision-free access by a subscriber station at least for certain periods of time 10 , 20th , 30th on a common channel is guaranteed.

The number and arrangement of the subscriber stations 10 , 20th , 30th in the bus system 100 of the exemplary embodiments is arbitrary. In particular, the subscriber station 20th in the bus system 100 omitted. It is possible that one or more of the subscriber stations 10 or 30th in the bus system 100 available. It is conceivable that all subscriber stations in the bus system 100 are designed the same, so only subscriber station 10 or only subscriber station 30th available.

The deterministic scheduling carried out by the scheduling units 15th , 25th , 35 is carried out, can be switched on or off at any time in order to be aware of the current operating status of the bus system 100 adapt. For example, deterministic scheduling is used in real-time operation. In contrast, deterministic scheduling can be switched off in the workshop when new firmware versions are loaded (flashed).

In addition or as an alternative, it is possible, when operating the deterministic time planning (scheduling), that the parameters SN, Ws described above are transferred by the time planning units 15th , 25th , 35 used, can be changed as required during operation.

Claims (20)

Subscriber station (10; 20; 30; 1 to 4) for a serial bus system (100), with a communication control device (11; 21; 31) for controlling communication between the subscriber station (10; 20; 30; 1 to 4) with at least one other subscriber station (10; 20; 30; 1 to 4) of the bus system (100), a transmitting / receiving device (12; 22; 32) for transmitting a transmission signal (TX1; TX2; TX3; TX4) generated by the communication control device (11; 21; 31) in a frame (450; 460) on a bus (40) of the bus system (100), and a time planning unit (15; 25; 35) for planning a temporal access of the subscriber station (10; 20; 30; 1 to 4) to the bus (40) in at least one time slot (S1 to S4) of a round (C) of consecutive times Time slots (S1 to S4), wherein at least one time slot (S1 to S4) is provided in a round (C) for each subscriber station (10; 20; 30; 1 to 4) of the bus (40) for sending its transmission signal (TX1; TX2; TX3; TX4) and the round (C) repeats itself cyclically, and wherein the time planning unit (15; 25; 35) is designed, using at least one piece of information received from the bus (40), to determine an assignment which defines which time slot (S1 to S4) of the round (C) the transmitting / receiving device (12; 22; 32) for sending the frame (450; 460) for the send signal (TX1; TX2; TX3; TX4) on the bus (40). Subscriber station (10; 20; 30; 1 to 4) Claim 1 , wherein the at least one piece of information received from the bus (40) is a frame notifying the start of the round (SOCR), and wherein the at least one piece of information received from the bus (40) also includes a frame identifier (451x) and / or a Assignment of the time slots (S1 to S4) of a round (C) to the subscriber stations (10; 20; 30; 1 to 4) of the bus (40) and / or includes the information which of the subscriber stations (10; 20; 30; 1 to 4) of the bus (40) is currently sending. Subscriber station (10; 20; 30; 1 to 4) Claim 1 or 2 , wherein the scheduling unit (15; 25; 35) is configured to use as the at least one piece of information received from the bus (40) at least the frame notifying the start of the round (SOCR) and a frame identifier (451x) of a sender of a evaluate the frame (450; 460) received from the bus (40). Subscriber station (10; 20; 30; 1 to 4) according to one of the preceding claims, wherein the time planning unit (15; 25; 35) is designed to evaluate a data field (DF) of the frame (SOCR) which notifies the start of the round, in which the at least one piece of information received from the bus (40) is arranged. Subscriber station (10; 20; 30; 1 to 4) Claim 1 or 2 , wherein the scheduling unit (15; 25; 35) is configured to wait until the communication control device (11; 21; 31) has received a frame notifying the start of the round (SOCR) from the bus (40) and is configured to follow this with the other subscriber stations (10; 20; 30; 1 to 4) of the bus (40) in the operation of the bus system (100) using a priority of the transmission signal (TX1; TX2; TX3; TX4) to determine which time slot (S1 to S4 ) the round (C) may use the transmitting / receiving device (12; 22; 32) to transmit the frame (450; 460) for the transmission signal (TX1; TX2; TX3; TX4) on the bus (40). Subscriber station (10; 20; 30; 1 to 4) according to one of the preceding claims, wherein the communication control device (11; 21; 31) is designed to at least in a switch-on phase (C_E) of the bus (40) the frame (450; 460) into a first communication phase (451) and a second communication phase (452), and wherein in the first communication phase (451) it is negotiated which of the subscriber stations (10, 20, 30) of the bus (40) gets an at least temporarily exclusive, collision-free access to the bus (40) in the subsequent second communication phase (452). Subscriber station (10; 20; 30; 1 to 4) Claim 6 , the number (SN) of time slots (S1 to S4) per round (C) being greater than the number of time slots (S1 to S4) which the subscriber stations (10; 20; 30; 1 to 4) of the bus (40 ) are assigned per round (C), and negotiation takes place in the first communication phase (451) in a time slot (S5) which is not assigned to any of the subscriber stations (10; 20; 30; 1 to 4) of the bus (40) , which of the subscriber stations (10, 20, 30) of the bus (40) in the subsequent second communication phase (452) receives an at least temporarily exclusive, collision-free access to the bus (40). Subscriber station (10; 30) after Claim 6 or 7th , wherein the minimum duration of a time slot (S1 to S4) is a bit time of a bit of the first communication phase (451), and wherein the scheduling unit (15; 25; 35) is optionally designed in a time slot (S1 to S4) which the Subscriber station (10; 20; 30; 1 to 4) is assigned to send a frame (450; 460) with a priority which is higher than a priority of a frame (450; 460) which the scheduling unit (15; 25; 35) is designed to send in a time slot (S1 to S4) which is assigned to another subscriber station (10; 20; 30; 1 to 4) of the bus (40). Subscriber station (10; 30) after Claim 6 or 7th , wherein the minimum duration of a time slot (S1 to S4) is two bit times of a bit of the first communication phase (451), and wherein the scheduling unit (15; 25; 35) is designed to allow the subscriber station (10; 20; 30; 1 to 4) on the bus (40) in the second bit (B2_S1) of a time slot (S1 to S4) of the round (C) when another subscriber station (10; 20; 30; 1 to 4) of the bus (40 ) in the first bit (B1_S1) of the time slot (S1 to S4) lets its transmission opportunity (TO) pass unused. Subscriber station (10; 20; 30; 1 to 4) according to one of the preceding claims, wherein the scheduling unit (15; 25; 35) has a counting module (151; 251; 351) which is designed to increment its count value for each frame (450; 460) received from the bus (40) and for each time slot (S1, S2, S3, S4) to increment unused elapsed transmission opportunity (TO), and wherein the counting module (151; 251; 351) is configured to set its count value to 1 when the frame notifying the start of the round (SOCR) has been received. Subscriber station (10; 20; 30; 1 to 4) Claim 10 wherein the counting module (151; 251; 351) is designed to increment its count value for each frame (450; 460) received from the bus (40) after receiving a bit which signals the start of a frame (450; 460), even if the frame (450; 460) is later aborted by the subscriber station (10; 20; 30; 1 to 4) sending the frame (450; 460) due to an error. Subscriber station (10; 20; 30; 1 to 4) Claim 10 or 11 , wherein the scheduling unit (15; 25; 35) is designed to allow the subscriber station (10; 20; 30; 1 to 4) to access the bus (40) for the next time slot (S1 to S4) of the round (C) to be released when the count value of the counting module (151; 251; 351) is equal to the number of the time slot (S1 to S4) assigned to the subscriber station (10; 20; 30; 1 to 4). Subscriber station (10; 20; 30; 1 to 4) according to one of the preceding claims, wherein the time planning unit (15; 25; 35) is designed to allow the subscriber station (10; 20; 30; 1 to 4) access to the bus over time (40) to be released in a time slot (S1 to S4) of the round (C) when the subscriber station (10; 20; 30; 1 to 4) or another subscriber station (10; 20; 30; 1 to 4) of the bus ( 40) lets their transmission opportunity (TO) pass unused. Subscriber station (10; 20; 30; 1 to 4) according to one of the preceding claims, wherein the communication control device (11; 21; 31) is designed to arrange a subscriber station number in the transmit signal (TX1; TX2; TX3; TX4) which is on the bus (40) exclusively for the subscriber station (10; 20; 30; 1 to 4) is assigned, and wherein the time planning unit (15; 25; 35) for enabling temporal access of the subscriber station (10; 20; 30; 1 to 4) to the bus (40) in the one assigned to the subscriber station (10; 20; 30; 1 to 4) Time slot (S1 to S4) of the round (C) is designed when the time planning unit (15; 25; 35) can evaluate a subscriber station number in a frame (450; 460) received from the bus. Subscriber station (10; 20; 30; 1 to 4) according to one of the preceding claims, the number of time slots (S1 to S4) assigned to the subscriber station (10; 20; 30; 1 to 4) per round (C) , is at least temporarily unequal to a number of time slots (S1 to S4) which are assigned to another subscriber station (10; 20; 30; 1 to 4) of the bus (40) per round (C). Subscriber station (10; 20; 30; 1 to 4) according to one of the preceding claims, wherein the subscriber station (10; 20; 30; 1 to 4) is designed to have more than one frame (450; 460) per time slot (S1 to S4) ) on the bus (40), and / or wherein the number of frames (450; 460) which the subscriber station (10; 20; 30; 1 to 4) per time slot (S1 to S4) on the bus (40 ) is allowed to send, is at least temporarily unequal to a number of frames (450; 460) that another subscriber station (10; 20; 30; 1 to 4) of the bus (40) per time slot (S1 to S4) on the bus (40 ) may send. Subscriber station (10; 20; 30; 1 to 4) according to one of the preceding claims, wherein the communication control device (11; 21; 31) is designed to send a dominant pulse (P) at the beginning of a recessive bit in the time slot assigned to the subscriber station, which is shorter than the bit time of the recessive bit (B1_S1) when the communication control device (11; 21; 31) lets its transmission opportunity (TO) pass unused. Subscriber station (10; 20; 30; 1 to 4) according to one of the preceding claims, wherein the subscriber station (10; 20; 30; 1 to 4) is designed such that the scheduling unit (15; 25; 35) depending on the time requirements to the communication on the bus (40) can be switched on or off, or that an operating mode of the time planning unit (15; 25; 35) can be changed by configuring predetermined parameters (SN, W) during operation of the bus system (100), wherein the operating mode of the scheduling unit (15; 25; 35) defines a predetermined mode of communication on the bus (40). Bus system (1), with a bus (40), at least two subscriber stations (10; 20; 30; 1 to 4) according to one of the preceding claims, wherein the at least two subscriber stations (10; 20; 30; 1 to 4) are connected to one another via the bus (40) in such a way that they are serially can communicate with each other, wherein at least one of the subscriber stations (10; 20; 30; 1 to 4) is a master subscriber station (10; 20; 30) for sending a frame (SOCR) which the at least two subscriber stations (10; 20; 30; 1 to 4) notifies the start of a round of communication on the bus (40), at least one backup master (10; 20; 30) being optionally provided for additionally performing the function of the master subscriber station (10; 20; 30) on the bus (40). Method for communication in a serial bus system (100), the method being carried out with a subscriber station (10; 20; 30; 1 to 4) of the bus system (100) which has a communication control device (11; 21; 31) and a transmission / Receiving device (12; 22; 32), the method comprising the steps of Controlling, with a communication control device (11; 21; 31), a communication of the subscriber station (10; 20; 30; 1 to 4) with at least one other subscriber station (10; 20; 30; 1 to 4) of the bus system (100), and Sending, with a transmitting / receiving device (12; 22; 32), a transmission signal (TX1; TX2; TX3; TX4) generated by the communication control device (11; 21; 31) in a frame (450; 460) on a bus ( 40) of the bus system (100) according to the planning of a time planning unit (15; 25; 35) which allows the subscriber station (10; 20; 30; 1 to 4) to access the bus (40) in at least one time slot (S1 to S4) plans a round (C) of consecutive time slots (S1 to S4), wherein at least one time slot (S1 to S4) is provided in a round (C) for each subscriber station (10; 20; 30; 1 to 4) of the bus (40) for sending its transmission signal (TX1; TX2; TX3; TX4) and the round (C) repeats itself cyclically, and wherein the scheduling unit (15; 25; 35) using at least one piece of information received from the bus (40) is able to determine an assignment which defines which time slot (S1 to S4) of the round (C) the transmission / Receiving device (12; 22; 32) for sending the frame (450; 460) for the transmission signal (TX1; TX2; TX3; TX4) on the bus (40).

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